Overspeed shut-off device for turbines



March 12, 1957 L. COHEN OVERSPEED SHUT-OFF DEVICE FOR TURBINES Filed March 7, 1956 DIRECTION OF ROTATION 2 Sheets-Sheet 1 INVENTOR. LEO- COHEN ATTORNEY March 12, 1957 COHEN 2,784,935

OVERSPEED SHUT-OFF DEVICE FOR TURBINES Filed March 7, 1.956 2 Sheets-Sheet 2 TO TURBINE VALVE OPENED FROM SOURCE FROM SOURCE IN VEN TO'R. LEO COHEN ATTORNEY Leo Cohen, Cleveland, Ohio,

United States Patent 2,784,935 OVERSPEED SHUT-OFF DEVICE FOR TURBINES assignor to Jack & Heintz, Ohio, a corporation of Delaware Application March 7, 1956, Serial No. 570,092 6 Claims. (Cl. 253-59) Inc., Cleveland,

This invention relates in general to fluid operated turbines and more particularly to improvements in devices for automatically shutting 01f the operating fluid supply to the turbine upon the latter attaining a predetermined speed of rotation, so as to prevent overspeed rotation of the turbine that might otherwise occur for any reason.

I am aware of the fact that it has been conventional practice to provide spring loaded valves in the fluid supply line from the turbine to the nozzle so designed that upon a predetermined fluid pressure the spring will be overcome and the nozzle closed by the valve.

One of the primary objects of my invention is to provide a highly sensitive device that will be responsive to the speed variable magnitude and direction of the dynamic pressure developed by the motive fluid as it leaves the rotatingblades ofthe turbine as the force necessary to actuate an electrical means for shutting oil, by valve means, the supply of operating pressure fluid from the source to the turbine. This is especially important when the turbine is used as the power source for air turbine starters for engines.

With this in mind, I propose to provide a cylinder that s sealed at one end and within which a close fitting piston 18 slidably mounted. One side of the piston is exposed to dynamic pressure of the turbine pressure fluid and the piston is spring loaded to oppose such pressure. The other side of the piston is exposed to a reference static pressure.

The cylinder is so positioned that its longitudinal axis intersects the rotating turbine axis at right angles. The cylinder is positioned adjacent to the turbine rotor and in the direct path of the pressure fluid leaving the turbine. A slot is cut in the cylinder transverse to its longitudinal axis and in a predetermined circumferential position such as to expose its interior to the dynamic pressure of the fluid when it leaves the turbine rotor at the absolute flow angle corresponding to the limiting overspeed condition and at all flow angles corresponding to progressively increasing speeds in excess of the limiting overspeed. The pressure fluid is admitted into the cylinder underneath the piston WhiCh I S spring-loaded to oppose any fluid pressure tending to raise the piston. The opposite side of the piston' is provided with a piston rod that is normally out of contact with a switch leaving the valve open between the source of pressure fluid and the turbine. When the pressure in the cylinder below the piston reaches a predetermined degree the piston will be forced upward- .ly against the action of the spring to bring the piston rod into contact with a suitable switch for energizing a suitable electrical circuit for closing the valve between the source of pressurefluid and the turbine so as to stop the rotation of the turbine.

With the .foregoing and other objects in View, the invention resides in the combination of the parts and in the details of construction hereinafter set forth in the following specification and appended claims, certain embodiments being illustrated in the accompanying drawings, in

which:

Figure 1 is a view in section taken through the cylinder of the valve shut-ofi' mechanism showing the piston and piston rod and the micro switch in elevation and also showing the piston rod out of engagement with the micro switch in which case the valve between the pressure fluid source and the turbine is open;

Figure 2 is a view similar to Figure 1, showing the piston to have been raised by the pressure fluid from the turbine against the opposition of the spring so as to bring the piston rod into a position to trip the micro switch in which case the valve between the pressure fluid source and the turbine is closed;

Figure 3 is a view in section taken along line 33.of Figure 1, through thecylinder below the piston, to show the slot cut in the cylinder in a predetermined relationship to the axis of rotation of the turbine, the blades of the turbine being shown diagrammatically to show their relationship with respect to the cylinder and the slot;

Figure 4 is a diagrammatical view showing the circuit between the micro switch and'the valve between the pressure fluid source and the turbine and also showing the valve cylinder and piston rod, the latter being shown out of contact with the micro switch in:the same relative positions as shown in Figure 1, in which case the valve between the pressure fluid source and the turbine is open; and

Figure 5 is a diagrammatical view similar to that of Figure 4, showing the cylinder, piston and piston rod in the same relative positions as shown in Figure 2, in which case the piston rod has actuated the micro switch to close the circuit so as to close the valve between the pressure fluid source and the turbine.

Referring more particularly to the drawings, I have shown the overspeed actuator to include a cylinder 1 in which is slottedly mounted a piston 2.. I may employ an adjustable screwplug 3 that is vertically adjustable in cylinder 1. Surrounding the piston rod 4 and disposed between the plug 3 and the upper side of piston 2 is a compression coil spring 5 that normally urges the piston 2 downwardly against a seat 6 in the form of an internal flange in the cylinder 1. It will be readily apparent that the compression force of the spring 5 urging the piston 2 downwardly against its seat may be readily adjustable bymeans of the screw plug 3. I have also shown the upper end of the piston rod 4 to be externally screwthreaded at 7 to adjustably receive a flanged collar 8 which when properly adjusted may be secured in such adjusted position by a screw 9. In Figure 1 the flange 8 is shown to be spaced and out of contact with the roller 10 of an arm 11 forming part of a suitable micro switch located in housing 12 that is supported by a stationary bracket 13.

As shown in Figure 3 the cylinder 1 is so positioned with respect to the axis of theturbine whose blades are shown at 14 that the longitudinalaxis of the cylinder intersects the turbine axis at right angles. The cylinder is positioned adjacent to the turbine rotor and is in the path of the fluid leaving the turbine, the path of the fluid being indicated by appropriate arrows. A slot 15 is cut in the cylinder so as to be transverse to the longitudinal axis of the cylinder and in a predetermined circumferennitude of the flow is increased but the direction of flow is also changed, as illustrated by arrows 17 as the fluid leaves the turbine to flow through the slot to enter the cylinder below the piston. As a matter of constructional refinement, I have shown the cylinder to be provided with a filter including a perforatedfrarne 18 in which I have located suitable filtering material 19.

In Figures 4- and 5 I have schematically illustrated an electrical circuit between the micro switch and the valve that is located between the pressure fluid source and the turbine. The relationship between the cylinder, piston, piston rod and micro switch shown in Figure 4 is the same as shown in Figure 1. At 20 I have shown a casing in which is located any suitable type of shut-off or on-off valve for controlling the flow of pressure fluid from a suitable source to the turbine. The circuit is such as to include an electrical source such as a direct current battery. As long as the piston is out of engagement with the micro switch the valve remains open so as to permit the flow of pressure fluid from the source to the turbine to permit the latter to operate at a speed responsive to the pressure of the fluid from the source. When, however, this pressure attains a predetermined degree the piston is raised from its seat against the opposition of spring 5 so as to bring the piston rod into a position where it trips the micro switch to close the circuit to actuate the Valve into a closed position so as to immediately shut off any further supply of pressure fluid from the source to the turbine source to stop the rotation of the turbine.

it is to be understood, of course, that a reduction in the degree of pressure from the source will permit the spring 5 to once again force the piston back down on its seat source to bring the piston rod out of engagement with the tripping lever of the micro switch so as to again open the valve to permit the resumption of operation of the turbine. When the turbine is used as a power source for an air turbine starter for engines, a suitable holding relay is preferably located in the electrical circuit, in which case a manual reset control button must be actuated by the operator for engine restarting purposes. The purpose of the exhaust port 21 is to permit escape of the pressure fluid from the cylinder above the piston as it is elevated in the two identical positions shown in Figures 2 and 5.

I claim:

1. In combination with a turbine, a pressure fluid source and a control valve between said source and said turbine, a device for closing said valve for stopping the turbine upon the turbine attaining a predetermined speed of rotation, said device including a cylinder and a piston slidably mounted therein, a seat in said cylinder for said piston, spring means to normally urge said piston against its seat, electrical means for actuating said valve in circuit with a switch that is normally open to maintain said valve normally open, a piston rod maintained by said spring to be out of contact with said switch, said cylinder having a slot that is transverse to its longitudinal axis and in a predetermined circumferential position such as to expose its interior below said piston to the variable magnitude and direction of the dynamic pressure of the fluid as it leaves the turbine, which when it reaches a predetermined degree raises said piston against the action of said spring means to close said switch through its piston rod to close said circuit to close said valve to stop the operation of said turbine. V

2. In combination with a rotary blade fluid turbine, a pressure fluid source and a control valve between said source and said turbine, a device for closing said valve for stopping the turbine upon the turbine attaining a predetermined spced of rotation, said device including a cylinder and a piston slidably mounted therein, a seat in said cylinder for said piston, spring means to normally urge said piston against its seat, electrical means for actuating said valve in circuit with a switch that is normally open to maintain said valve normally open, a piston rod maintained by said spring to be out of contact with said switch, said cylinder having a slot that is transverse to its longitudinal axis and in a predetermined circumferential position such as to expose its interior below said piston to the variable magnitude and direction of the dynamic pressure of the fluid as it leaves the turbine blades, which when it reaches a predetermined degree raises said piston against the action of said spring means to close said switch through its piston rod to close said circuit to close said valve to stop the rotation of said turbine. t

3. In combination with a rotary blade fluid turbine, a pressure fluid source and a control valve between said source and said turbine, a device for closing said valve for stopping the turbine upon the turbine attaining a predetermined speed of rotation, said device including a cylinder and a piston slidably mounted therein, a seat in said cylinder for said piston, spring means to normally urge said piston against its seat, electrical means for actuating said valve in circuit with a switch that is normally open to maintain said valve normally open, a piston rod maintained by said spring to be out of contact with said switch, said cylinder being positioned adjacent to said turbine and in the path of fluid leaving said turbine, said cylinder having a slot that is transverse to its longitudinal axis and in a predetermined circumferential position such as to expose its interior below said piston to the variable magnitude and direction of the dynamic pressure of the fluid as it leaves the turbine blades, which when it reaches a predetermined degree raises said piston against the action of said spring means to close said switch through its piston rod to close said circuit to close said valve to stop the rotation of said turbine.

4. In combination with a rotary blade fluid turbine, a pressure fluid source and a control valve between said source and said turbine, a device for closing said valve for stopping said turbine upon the turbine attaining a predetermined speed of rotation, said device including a cylinder and a piston slidably mounted therein, a seat in said cylinder for said piston, spring means to normally urge said piston against its seat, electrical means for actuating said valve in circuit with a switch that is normally open to maintain said valve normally open, a piston rod maintained by said spring to be out of contact with said switch, said cylinder being so positioned that its longitudinal axis intersects the axis of rotation of said turbine at right angles, said cylinder having a slot that is transverse to its longitudinal axis and in a predetermined circumferential position such as to expose its interior below said piston to the Variable magnitude and direction of the dynamic pressure of the fluid as it leaves the turbine blades, which when it reaches a predetermined degree raises said piston against the action of said spring means to close said switch through its piston rod to close said circuit to close said valve to stop the rotation of said turbine.

5. In combination with a rotary blade fluid turbine, a pressure fluid source and a control valve between said source and said turbine, a device for closing said valve for stopping said turbine upon the turbine attaining a predetermined speed of rotation, said device including a cylinder and a piston slidably mounted therein, a seat in said cylinder for said piston, spring means to normally urge said piston against its seat, electrical means for actuating said valve in circuit with a switch that is normally open to maintain said valve normally open, a piston rod maintained by said spring to be out of contact with said switch, said cylinder being so positioned that its longitudinal axis intersects the axis of rotation of said turbine at right angles, said cylinder being positioned adjacent to said turbine and in the path of fluid leaving said turbine, said cylinder having a slot that is transverse v to its longitudinal axis and in a predetermined circumferential position such as to expose its interior below said piston to the variable magnitude and direction of the dynamic pressure of the fluid as it leaves the turbine blades, which when it reaches a predetermined degree raises said piston against the action of said spring means to close said switch through its piston rod to close said circuit to close said valve to stop the rotation of said turbine.

6. In combination with a rotary blade fluid turbine, a pressure fluid source and a control valve between said source and said turbine, a device for closing said valve for stopping said turbine upon the turbine attaining a predetermined speed of rotation, said device including a 10 cylinder and a piston slidably mounted therein, a seat in said cylinder for said piston, an adjustable screw plug in said cylinder and a compression coil spring between said plug and said piston to normally urge said piston against its seat, electrical means for actuating said valve 15 in circuit with a micro switch that is normally open to maintain said valve normally open, a piston rod main tained by said spring to be out of contact with said switch, said cylinder being so positioned that its longitudinal axis intersects the axis of rotation of said turbine at right angles, said cylinder being positioned adjacent to said turbine and in the path of fluid leaving said turbine, said cylinder having a slot that is transverse to its longitudinal axis and in a predetermined circumferential position such as to expose its interior below said piston to the variable magnitude and direction of the dynamic pressure of the fluid as it leaves the turbine blades, which when it reaches a predetermined degree raises said piston against the action of said spring to close said switch through its piston rod to close said circuit to close said valve to stop the rotation of said turbine.

No references cited. 

